It was a stunning fall from grace for one of the biggest US media names, a veteran broadcaster at Fox News for two decades, who counted President Donald Trump among his personal supporters and whose ratings had soared regardless of alleged abusive behavior towards women dating back years.

But the departure of major advertisers, worried about the knock-on effect of being associated with "The O'Reilly Factor," ultimately sealed his fate as the Murdoch family, which owns the corporation, flexes their might in a global marketplace.

"After a thorough and careful review of the allegations, the company and Bill O'Reilly have agreed that Bill O'Reilly will not be returning to the Fox News Channel," 21st Century Fox said in simple, one-sentence statement.

The announcement came just hours after the combative and right-wing television personality was photographed shaking hands with Pope Francis in St Peters Square, wearing a suit and tie, on holiday in the Italian capital.

Beset by scandal for weeks, the 67-year-old told viewers on April 11 that he was taking a "long-planned break" but originally said he would return on April 24.

O'Reilly had rarely been out of the headlines since a New York Times investigation revealed on April 1 that he and Fox paid five women a total of $13 million in cases spanning 15 years, in exchange for silence about his alleged behavior.

He never directly denied the allegations, saying he was "vulnerable to lawsuits from individuals who want me to pay them to avoid negative publicity."

Commentators said his dismissal marked a defining point for Fox, less than a year after Roger Ailes, the 76-year-old former executive who built up the channel, resigned under a haze of similarly damaging sexual harassment accusations.

- Down to money -

But the endorsement of a Republican commander-in-chief -- himself caught on tape in 2005 boasting of groping women and now saddled with record-low approval ratings less than 100 days into his presidency -- was not enough to right the ship for O'Reilly.

Scores of companies yanked advertising from his show, the most popular in US cable news watched on average by 3.98 million viewers in early 2017, according to Adweek.

Jane Hall, a journalism professor at American University in Washington and former Fox News contributor called it a "significant moment" in dealing with allegations of sexual harassment, both at Fox News and in general.

She (Munich: SOQ.MU - news) pointed to a generational split between Rupert Murdoch, the Australian-born media baron traditionally hands-off in such cases and his adult sons, James and Lachlan, taking on an increasingly powerful role.

"The fact that advertisers began to take themselves out of the program and made statements that they did not want to be associated with allegations of sex harassment and supported women in the workplace was a significant moment," she said.

Paul Janensch, a former newspaper editor and retired journalism professor at Quinnipiac University, said in the end it came down to money and the "paradox" that while ratings were up, advertisers were fleeing in their droves.

"It's a business and if the pushback... was going to hurt Fox's bottom line then he's gone," he told AFP.

Fox occupies a unique and powerful if controversial, position in America -- watched by a deep and committed conservative fan base that to a large extent includes many of those who voted Trump into office last year.

"The more biased and slanted it is, the more they like it. These are people who want prejudices reinforced," said Janensch.

While the relationship between Trump and Fox has had rough patches, particularly during last year's election, the Republican White House is having a boom effect on Fox -- and indeed other television -- ratings.

All eyes will now focus on O'Reilly's replacement. During his vacation, his show had been hosted by a rotating cast of substitutes, including Dana Perino, former spokeswoman for president George W. Bush.